In the prior art, proposals have existed for a long time for changeover systems which are suited, by the exchange of particular components, to converting a weapon which is originally provided for example for a larger caliber into a weapon for ammunition having a smaller caliber. This is expedient in particular in order to provide a weapon in this way by which more favourably-priced small-caliber ammunition is fired for practice purposes, wherein the conversion to the large-caliber weapon of the original type is to be able to be carried out with as little effort as possible. Such a weapon is described in U.S. Pat. No. 5,461,811, in which the magazine is exchanged, wherein the replacement magazine for small-caliber ammunition has the same external dimensions as the original magazine for the large-caliber ammunition, so that there is a certain compatibility in the respective magazines. However, in the case of this weapon it is necessary to also exchange the barrel and housing on changing the caliber for adaptation to the new caliber, wherein these components generally have different dimensions. The named publication does not contain any actual embodiments for this.
In U.S. Pat. No. 6,276,252 B1 a firearm is described, in which a training barrel is used for the conversion to small-caliber ammunition. Whereas when shooting with large-caliber ammunition the barrel slides back a certain distance with the slide after the shot, when shooting small-caliber ammunition, there is no locking between the barrel and the slide, so that the training barrel does not move back on firing. As the intermediate space between the inlet of the cartridge chamber and the upper side of the magazine is too great when using the training barrel, with this use an extension of the feed ramp in the form of a separate component is inserted into the weapon. In such a known firearm, however, there is an aim that it can be converted comparatively simply by the user from the variant with training barrel into the original large-caliber weapon by changing the barrel and removing the feed ramp extension. When the barrel for the smaller caliber is exchangeable with the corresponding components of a large-caliber weapon of the same type of construction, it cannot be prevented that the owner of a small-caliber weapon converts this to a large-caliber weapon by exchanging the barrel, which, however, is questionable due to the different legal provisions concerning weapons. The known solution therefore only applies to persons who legally own a large-caliber weapon and for example shoot with this small-caliber ammunition for training purposes.